272 TlMEHRI. 
Museum, the labarria (Trigonocephalies atrox)> and the 
rattlesnake (Crotalus horridus), of both of which species, 
spirit specimens have been already noticed in the case, 
are the most to be feared, and the deadliest in the 
colony. They are peculiar from the fa6l that they 
have a pit on each side behind the nostrils, from which 
they have obtained the name pit- vipers — a charafter 
that is used to mark the family (Crotalidds) to which 
the American vipers belong. The horny rattle at the 
end of the tail of the rattlesnake is well known. 
Both the bushmaster and the labarria shew horny spines, 
representative of this rattle, at the end of the tail, and 
the spine from a labarria is shewn in the case. It is 
almost needless to say that this horny spine is perfectly 
harmless. The fangs alone carry death — the forked 
tongue, which is popularly called the sting, being also a 
perfectly harmless organ. 
The poison of snakes is but a modified form of saliva 
or spittle, and the glands modified salivary glands, from 
which the secretion is forced out by the pressure of 
muscles during the opening of the mouth. The channel 
in the fang is never a real perforation of the tooth. It 
results from the folding of the sides of the tooth, so to 
speak ; and the line of union ot the edges is always more 
or less visible in the tooth. In the poisonous Colubrine 
snakes with ere6l fangs, such as the cobras and the 
poisonous coral snakes, the tooth is only grooved to form 
a poison-channel : in the vipers, the edges of the groove 
unite and form a closed channel. 
The visitor having now inspected the various classes of 
objects, it might be advisable to sum up the position of 
the various kinds of animals in the scale of organisation. 
